1. Field of the Invention
The present invention relates to an apparatus and method for measuring fat thickness, and more particularly, to an apparatus and method for measuring fat thickness in a part of a human body by radiating light at the body part.
2. Description of the Related Art
The human body is mainly comprised of four components: water, protein, fat, and minerals. The ratio of these components in the body is different depending on sex, age, and race, but it is roughly 55:20:20:5. The ratio of the four components can be obtained from the amount of water in the body since protein and water are major components of human muscle and are proportional to each other. For example, if healthy muscle is comprised of about 73% water, the other 27% is protein. Minerals form bones, a weight of which is closely related with the muscle weight. In detail, the amount of protein and the amount of minerals can be obtained using the amount of water in the body, and the amount of fat in the body is obtained by subtracting the sum of the amounts of water, protein, and minerals from the body weight. Conventionally, bioelectrical impedance analysis (BIA) is most widely used to measure body fat. Besides, hydrodensitometry is also used.
In the BIA, a body fat rate is measured based on the fact that the amount of hydrodensitometry water in the body is inversely proportional to the electrical resistance of the body. The BIA is advantageous in that measurement is simple, quick, and non-invasive. When a weak alternating current (AC) electrical signal is applied to the human body, electricity flows along water having high conductivity in the body. According to the amount of water, the size of a passage through which the electricity flows is determined. A value measured in this situation indicates the bio-impedance. In calculating the amount of a body component using the bio-impedance, an AC of about 1 mA in a frequency band of 50 kHz is applied to the human body. When the AC flows in the body, body resistance is measured and the amount of water in the body is obtained using the body resistance. The amount of protein and the amount of minerals are obtained using the amount of water. A body fat rate is obtained using the amounts of protein and minerals and the weight of the body.
FIG. 1 is a perspective view of a conventional apparatus for measuring a body fat rate using near infrared rays. The apparatus radiates near infrared rays at a human body and measures a body fat rate. To accurately measure the body fat rate, near infrared rays must be uniformly radiated at a target body part and a constant amount of near infrared rays must be radiated at every measurement. The apparatus shown in FIG. 1 radiates near infrared rays at a target body part using four light emitters 100, 110, 120, and 130. To increase uniformity of radiation of near infrared rays, it is necessary to increase the number of light emitters or the length of the apparatus.
FIG. 2 illustrates a perspective view of another conventional apparatus for measuring a body fat rate using near infrared rays, to explain a method of setting a measurement position of the apparatus. For continuity of near infrared rays at every measurement, two marks 210 and 220 of the apparatus 200 must be always aligned when measurement is performed.
As described above, in the conventional apparatuses and methods for measured fat, it is necessary to increase the number of light emitters or the length of a measuring apparatus to satisfactorily uniformize the amount of near infrared rays radiated at a target body part. As a result, manufacturing cost increases and miniaturization cannot be accomplished. In addition, the conventional technology is inconvenient because a measurement position must be set at every measurement. Moreover, a fat rate in a whole human body can be measured, but the amount of fat in a part of the body cannot be measured.